1. 4/11/40 page 1 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Computer and Data Communications

2. 4/11/40 page 2 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL A Communications Model output information Input device Input device Transmiter Transmission medium Transmission medium Receiver Output Devices Output Devices input information input data transmitted signal received signal output data data : A represent of facts, concepts in a formalized manner suitable for communication information : The meaning that is currently assigned to data by means of the conventions applied to those data

3. 4/11/40 page 3 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Communication Tasks Transmission system utilization Interfacing Signal generation Exchange management Error detection and correction System management Flow control Addressing Routing Recovery Message formatting Protection

4. 4/11/40 page 4 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Data Communication Network Communication Network Communication Network Node Network Station

5. 4/11/40 page 5 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Data communication networks Public Switched Telephone Network (PSTN) Local Area Network (LAN) Leased lines Public switched data network (PSDN) Integrated services digital network (ISDN)

6. 4/11/40 page 6 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL PSTN modem modem link via PSTN PSTN

7. 4/11/40 page 7 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL LANhub hub hub hub 1st floor 2nd floor 3rd floor 4th floor router confined geographical area confined geographical area under single management under single management high data rate high data rate server station station station

8. 4/11/40 page 8 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Leased lines Lease pubic circuits to connect different sites Communication channel is privated LAN Voice LAN Voice LAN Voice leased circuit

9. 4/11/40 page 9 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL PSDN PSDN= Public Switched Data Network = LAN PSDN PSDN is designed specifically for the transmission of data rather than voice Comunication is shared

10. 4/11/40 page 10 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL ISDN ISDN NTE NTE = Network termination equipment ISDN = Integrated services digital network Using ISDN to carry both voice and data

11. 4/11/40 page 11 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Computer Communication Architecture Communication-related messages Network interface File and file transfer command Communication network File transfer application Communications service module Network access module Computer A File transfer application Communications service module Network access module Computer B

12. 4/11/40 page 12 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Three-layers model Applications Transport Network access

13. 4/11/40 page 13 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Communication architectures and networks Applications Transport Network access 1 2 3 4 ( ) ( ) Applications Transport Network access 1 2 3 ( ) ( ) ( ) Applications Transport Network access 1 2 ( ) Communication network Service Access Point Network Address

14. 4/11/40 page 14 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Protocol layers Computer B Transport protocol Network Access Protocol Application protocol Application Transport Network access Computer A Application Transport Network access Computer B

15. 4/11/40 page 15 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Protocol data unit Application data Application data Transport header Transport header Transport header Transport header Network header Network header Transport protocol data unit (TPDU) Network protocol data unit (NPDU) Application data Application data Application data control info + data in each layer = protocol data unit (PDU)

16. 4/11/40 page 16 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL OSI reference Model Layer 1 Physical link Layer 2 Data link layer Layer 3 Network layer Layer 4 Transport layer Layer 5 Session layer Layer 6 Presentation layer Layer 7 Application layer developed by ISO

17. 4/11/40 page 17 Department of Computer Engineering, Kasetsart University 204325 Introduction to Computer Communications and Networks CONSYL Standards Integrated computer and telecommunications industry Integrated computer and telecommunications industry ISO ITU-T International Standards (Open systems interconection) Telecommunications Industry Telecommunications Industry ITU-T CEPT ANSI Interface standards (multi-vendor systems) Computer Industry Computer Industry Proprietary standards (closed systems) ECMA EIA IEEE